Drilling on gauge sub

ABSTRACT

A drilling on gauge sub including a tubular housing having a first end, a second end and an exterior surface. Coupling means are positioned at both the first end and the second end of the tubular housing to couple the tubular housing to other components of a drill string. At least three cavities are provided in the exterior surface of the tubular housing. Each of the cavities having a first end and a second end. Reamer cutters are secured within each of the at least three cavities. The reamer cutters including cutters mounted on rotatably mounted rollers.

FIELD OF THE INVENTION

The present invention relates to a drilling on gauge sub.

BACKGROUND OF THE INVENTION

As a drill bit wears during drilling, the hole it makes becomesundergauged. When the hole is undergauged there is a danger that thedrill string behind the bit will become stuck. In order to minimize theamount of undergauged hole, a sub having reamer cutters is positioneddirectly behind the drill bit. As the drill bit wears, the reamercutters of the drilling on gauge sub enlarge the hole made by the drillbit to keep the hole “on gauge”. When the drill bit is replaced due towear, the drilling on gauge sub is also replaced due to wear of thereamer cutters. A problem currently being experienced when drilling ongauge is high torque loading. This torque loading can become so severeas to result in the drill string becoming stuck in the hole.

SUMMARY OF THE INVENTION

What is required is a drilling on gauge sub that will not create as muchtorque loading of the drill string.

According to the present invention therefore provided a drilling ongauge sub which includes a tubular housing having a first end, a secondend and an exterior surface. Coupling means are positioned at both thefirst end and the second end of the tubular housing to couple thetubular housing to other components of a drill string. At least threecavities are provided in the exterior surface of the tubular housing.Each of the cavities having a first end and a second end. Reamer cuttersare secured within each of the at least three cavities. The reamercutters including cutters mounted on rotatably mounted rollers.

With the drilling on gauge sub, as described above, the rollers serve asa bearing surface which guides the bit on the downhole drilling motor.This greatly reduces the torque required to drilling a gauged hole witha downhole drilling motor.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become more apparent fromthe following description in which reference is made to the appendeddrawings, the drawings are for the purpose of illustration only and arenot intended to in any way limit the scope of the invention to theparticular embodiment or embodiments shown, wherein:

FIG. 1 is a side elevation view, in section, of a drilling on gauge subconstructed in accordance with the teachings of the invention;

FIG. 2 is a side elevation view of a drill string to which the drillingon gauge sub illustrated in FIG. 1 is coupled;

FIG. 3 is a side elevation view in section of a reamer cutter modulefrom the drilling on gauge sub illustrated in FIG. 1;

FIG. 4 is a side elevation view, in section, of the drilling on gaugesub illustrated in FIG. 1, with the reamer cutter module removed; and

FIG. 5 is an end view, in section, of the drilling on gauge subillustrated in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment, a drilling on gauge sub generally identifiedby reference numeral 10, will now be described with reference to FIGS. 1through 5.

Structure and Relationship of Parts:

Referring now to FIG. 1, drilling on gauge sub 10 has a tubular housing12 with a first end 14, a second end 16 and an exterior surface 18. Atboth first end 14 and second end 16 of housing 12, there is couplingmeans 20 to couple tubular housing 12 to other components of a drillstring 100. FIG. 2 shows drill string 100 with drilling on gauge sub 10connected in line. Referring to FIG. 5, there are three cavities 22 inexterior surface 18 of tubular housing 12. Referring to FIG. 4, eachcavity 22 has a first end 24 and a second end 25. At first end 24 ofcavity 22, there is an undercut locking groove 26. At least three reamercutter modules 28, are provided to be installed in cavity 22, where,referring to FIG. 1, each reamer cutter module 28 has a first end 30 anda second end 32. First end 30 of reamer cutter module 28 has aprojecting tongue 34 adapted to engage locking groove 26 of cavity 22.This arrangement allows reamer cutter module 28 to be inserted intocavity 22, with first end 30 secured by locking groove 26, while secondend 32 of reamer cutter module 28 is secured by detachable fasteners 36within second end 25 of cavity 22. This is done such that projectingtongue 34 of each reamer cutter module 28 remains locked in engagementwith locking groove 26, and such that each reamer cutter module 28 isfield replaceable by detaching fastener 36 and withdrawing projectingtongue 34 from locking groove 26. Reamer cutter modules 28 include pins29 to help keep the assembly together during installation andreplacement.

Detachable fasteners 36 are bolts 38 which engage threaded apertures 40in tubular housing 12. A debris cover 40 may also be positioned overeach bolt 38 which is adapted to shield bolt 38 from debris 42, shown inFIG. 2. Again referring to FIG. 1, debris cover 41 may be held in placeby a spring pin 44.

Referring now to FIG. 3, reamer cutter module 28 is shown to includecutters 46 rotatably mounted on rollers 48. Rollers 48 are cylindricalrollers oriented substantially parallel to the longitudinal axis 50 oftubular housing 12. Carbide spacers 52 are positioned at each end 54 ofcylindrical rollers 48 to serve as wear surfaces and transmit axialloads. Rollers 48 rotate on radial bearings 56, which are positionedwithin a lubricant filled bearing chamber 58 with seals 60 positioned ateach end 62 of bearing chamber 58 to contain lubricant 66. A lubricantsupply passage 68 is in communication with bearing chamber 58 with apiston 70 positioned in lubricant supply passage 68. Piston 70 has afirst face 72 and a second face 74. First face 72 engages lubricant 66contained within lubricant supply passage 68. Second face 74 is exposedto pressure from drilling fluids such that the pressure exerted uponsecond face 74 of piston 70 causes piston 70 to move in lubricant supplypassage 68 with first face 72 of piston 70 urging lubricant 66 intobearing chamber 58.

Operation:

The use of drilling on gauge sub 10 will now be discussed with referenceto FIGS. 1 to 5. Referring now to FIG. 1, reamer cutter modules 28 areinstalled in housing 12. Referring to FIG. 2, drilling on gauge sub 10is coupled by coupling means 20 into drill string 100. During drilling,drilling on gauge sub 10 ensures that the hole 78 drilled is the propergauge. Rollers 48 serve as a bearing surface which reduces frictionwhile guiding the drill bit of the downhole drilling motor. Referringagain to FIG. 1, when reamer cutter modules 28 are to be replaced, suchas when they are worn, or during a regular maintenance schedule, theyare removed by removing debris cover 40 held in place by spring pin 44and then removing bolt 38. First end 30 of reamer cutter module 28 isthen free to be removed by disengaging projecting tongue 34 from lockinggroove 26. Another reamer cutter module 28 may then be installed byreversing the procedure.

The drawings accompanying this application illustrate three cavities. Itwill be appreciated that there could be more than three cavities—withconfigurations of four, five, six, etc. The drawings accompanying thisapplication illustrate one type of cutter. It will be appreciated by oneskilled in the art that different cutters are used for hard formationsthan for soft formations. Since the tool is field serviceable, it may bedesirable to switch to different types of cutters when the tool is usedin different formations. Alternatively, one can have an even number ofcavities (four, six, or eight) with the cutters alternating around thecircumference of the tool between hard formation cutters and softformation cutters. This alternating configuration would be suitable forboth soft and hard formations.

In this patent document, the word “comprising” is used in itsnon-limiting sense to mean that items following the word are included,but items not specifically mentioned are not excluded. A reference to anelement by the indefinite article “a” does not exclude the possibilitythat more than one of the element is present, unless the context clearlyrequires that there be one and only one of the elements.

It will be apparent to one skilled in the art that modifications may bemade to the illustrated embodiment without departing from the spirit andscope of the invention as hereinafter defined in the Claims.

1. A drilling on gauge sub, comprising: a tubular housing having a firstend, a second end and an exterior surface; coupling means at both thefirst end and the second end of the tubular housing to couple thetubular housing to other components of a drill string; at least threecavities in the exterior surface of the tubular housing, each of thecavities having a first end and a second end; reamer cutters positionedin each of the at least three cavities, the reamer cutters includingcutters mounted on rotatably mounted rollers.
 2. The drilling on gaugesub as defined in claim 1, wherein the reamer cutters are in the form ofreplaceable modules detachably secured in the cavities by fasteners. 3.The drilling on gauge sub as defined in claim 2, wherein an undercutlocking groove is positioned at the first end of each of the cavities;each reamer cutter module having a first end and a second end, the firstend the each reamer cutter module having a projecting tongue adapted toengage the locking groove of one of the cavities; detachable fastenerssecuring the second end of each of the reamer cutter modules within thesecond end of one of the cavities so that the projecting tongue of eachreamer cutter module remains locked in engagement with the lockinggroove, each reamer cutter module being replaceable by detaching thefastener and withdrawing the projecting tongue from the locking groove.4. The drilling on gauge sub as defined in claim 1, wherein the rollersare cylindrical rollers oriented substantially parallel to thelongitudinal axis of the tubular housing.
 5. The drilling on gauge subas defined in claim 4, wherein carbide spacers are positioned at eachend of the cylindrical rollers to serve as wear surfaces and transmitaxial loads.
 6. The drilling on gauge sub as defined in claim 3, whereinthe detachable fasteners are bolts which engage threaded apertures inthe tubular housing.
 7. The drilling on gauge sub as defined in claim 6,wherein a debris cover is positioned over each of the bolts, the debriscover being adapted to shield the bolt from debris.
 8. The drilling ongauge sub as defined in claim 7, wherein each debris cover is held inplace by spring pins.
 9. The drilling on gauge sub as defined in claim1, wherein the rollers rotate on radial bearings.
 10. The drilling ongauge sub as defined in claim 9, wherein the radial bearings arepositioned within a lubricant filled bearing chamber with seals beingpositioned at each end of the bearing chamber to contain lubricant. 11.The drilling on gauge sub as defined in claim 10, wherein a lubricantsupply passage communicates with the bearing chamber, a piston beingpositioned in the lubricant supply passage, the piston having a firstface and a second face, the first face engaging lubricant containedwithin the lubricant supply passage, the second face being exposed topressure from drilling fluids, such the pressure; exerted upon thesecond face of the piston causes the piston to move in the lubricantsupply passage with the first face of the piston urging lubricant intothe bearing chamber.
 12. A drilling on gauge sub, comprising: a tubularhousing having a first end, a second end and an exterior surface; afirst coupling at the first end and a second coupling at the second endof the tubular housing, the first coupling and the second coupling beingadapted to couple the tubular housing to other components of a drillstring; more than two cavities in the exterior surface of the tubularhousing, each of the cavities having a first end and a second end, anundercut locking groove being positioned at the first end of each of thecavities; replaceable reamer cutter modules detachably positioned in thecavities, each reamer cutter module having a first end and a second end,the first end the each reamer cutter module having a projecting tongueadapted to engage the locking groove of one of the cavities, detachablefasteners securing the second end of each of the reamer cutter moduleswithin the second end of one of the cavities so that the projectingtongue of each reamer cutter module remains locked in engagement withthe locking groove, each reamer cutter module being replaceable bydetaching the fastener and withdrawing the projecting tongue from thelocking groove, each reamer cutter module including rotatably mountedcylindrical rollers which rotate on radial bearings and are orientedsubstantially parallel to the longitudinal axis of the tubular housing,cutters projecting from and being spaced around the outer circumferenceof the rollers; the radial bearings being positioned within a lubricantfilled bearing chamber with seals being positioned at each end of thebearing chamber to contain lubricant; and a lubricant supply passagecommunicates with the bearing chamber, a piston being positioned in thelubricant supply passage, the piston having a first face and a secondface, the first face engaging lubricant contained within the lubricantsupply passage, the second face being exposed to pressure from drillingfluids, such the pressure; exerted upon the second face of the pistoncauses the piston to move in the lubricant supply passage with the firstface of the piston urging lubricant into the bearing chamber.
 13. Thedrilling on gauge sub as defined in claim 12, wherein carbide spacersare positioned at each end of the cylindrical rollers to serve as wearsurfaces and transmit axial loads.
 14. The drilling on gauge sub asdefined in claim 12, wherein the detachable fasteners are bolts whichengage threaded apertures in the tubular housing.
 15. The drilling ongauge sub as defined in claim 14, wherein a debris cover is positionedover each of the bolts, the debris cover being adapted to shield thebolt from debris.
 16. The drilling on gauge sub as defined in claim 15,wherein each debris cover is held in place by spring pins.
 17. A methodof drilling on gauge with a downhole drilling motor assembly, comprisingthe steps of: securing a drilling on gauge sub having rollers on whichare secured cutters adjacent to a drill bit end of the downhole drillingmotor assembly; and using the cutters to ream the hole, while therollers concurrently guide the movement of the drilling motor assemblyand reduce friction with the hole.